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Author Topic: Birds Eye View  (Read 5307 times)

donamese

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Birds Eye View
« on: March 21, 2013, 10:10:18 AM »
New to the forum and using a GPS.  Finally upgraded from an old etrex to an Oregon 450t.  I am very interested in the satellite imagery but confused as to how it all works.  I only have the base 100K maps that came with the GPS, do I need to upgrade the maps to get better detail with the Birds Eye View?  Will the Birds Eye View work with the 24K Arizona maps offered on this site?  I am only worried about Arizona as that is the only place I consistently hunt. 

Seldom

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Re: Birds Eye View
« Reply #1 on: March 21, 2013, 10:43:24 AM »
Only Garmin proprietary maps will provide 3D views.  I don't own any BirdsEye (1 word) maps, but I'm pretty sure they are raster maps (satellite or raster topo) without elevation data built in.  If you want 3D you'll need to buy Garmin 24k topos.  If you can live with just very high quality 2D topos, download from this site, and save your money.  Keep in mind that no GPSr is reliable in canyons, and 3d won't help you there except in trip planning.  I walked Rim to Rim (from North Rim to Grand Canyon Village via Phantom Ranch), and my 62s added about 2 miles to my tracklog due to multipath and missing satellite errors.

donamese

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Re: Birds Eye View
« Reply #2 on: March 21, 2013, 10:51:41 AM »
Thank You.  I like the satellite images more for the fact I can see if water holes, clearings, dense trees, etc that may be near.  Basically the ability to scout on the fly when plan A or B fail while hunting.   Elevation isn't a huge concern to me as I can get a general idea from a topo. 

Boyd

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Re: Birds Eye View
« Reply #3 on: March 21, 2013, 10:52:09 AM »
"Birdseye" is indeed raster imagery, either aerial photography:

https://buy.garmin.com/shop/shop.do?pID=70144

Or scans of paper USGS 1:24000 topo maps:

https://buy.garmin.com/shop/shop.do?pID=98816

They are purchased separately for $30 which gives you one year of unlimited downloads. You can continue using what you have downloaded after the subscription expires. These have nothing to do with any other maps installed on your GPS. However, if you enable the topo on your 450t at the same time as the satellite imagery, the roads, streams, poi's, etc will also appear on your screen.

Is that what you mean, or are you asking about 3d views of your existing maps? You can view them in 3d (using newer versions of basecamp) but any maps from this site will just look "flat" whereas the topo on your 450t will show mountains rising from the surface. There are no tools for the makers of free maps that can create 3d terrain like Garmin uses in their own products.

donamese

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Re: Birds Eye View
« Reply #4 on: March 21, 2013, 11:00:13 AM »
Just looking for the Google Earth type view but wasn't sure if the BirdsEye was 24k or if it just layers on whatever Garmin map I had (which is 100K that are preloaded). 

Boyd

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Re: Birds Eye View
« Reply #5 on: March 21, 2013, 12:34:14 PM »
It is raster imagery. That's a fancy way of saying "pictures". This has nothing to do with your 100k map or the 24k map products that Garmin sells. These are known as vector based maps, and they consist of a list of coordinates where the GPS "connects the dots" to form a map.

You can turn off all the other maps on the GPS and use Birdseye, it does not depend on any other map.

Seldom

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Re: Birds Eye View
« Reply #6 on: March 21, 2013, 01:38:11 PM »
It is raster imagery. That's a fancy way of saying "pictures".

True, but to elaborate, the "pictures" will be georeferenced so that the GPSr can show your position accurately with reference to the imagery, so the imagery and the vector map will occupy the same place on the ellipsoid we call "The Earth".

Boyd

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Re: Birds Eye View
« Reply #7 on: March 21, 2013, 04:55:49 PM »
It may also help to have some understanding of the term "24k". This refers to printed paper maps where the scale is 1:24000. In other words, one inch on the map equals 24,000 inches (2,000 feet) in the real world. A 100k map would be 1:100,000 or 1 inch equals 100,000 inches (a little over 1.5 miles). As you can see, a 24k map would be much more accurate than a 100k.

In the digital world, this gets a little murkier because we are looking at the maps on a video screen where we can zoom in and out, instead of printed paper at a fixed scale. And there is no standard for how many pixels per inch on video screens.

But 24 x 4 is roughly equal to 100, so that would imply a 24k map has 4x the amount of detail. But really, it's much more because maps have width x height and we need to compare the area which is a squared function. So it would actually be 4 squared (4x4=16). In theory, a 24k map is capable of representing 16x the detail of a 100k map.

With satellite imagery, we think in terms of how many feet (or meters) is represented by each pixel on your screen. Garmin's Birdseye imagery is about 2 feet per pixel. This is way more detail than a 24k map has. I have made my own raster based maps from USGS 24k maps, and found that 10 feet per pixel was required to clearly see all the detail. So to compare Birdseye to a 24k map, the calculation would 10 ft per pixel / 2 ft per pixel = 5 ^2 = 25.

Therefore, assuming a nice clear photo, Birdseye can provide 25x the amount of detail as a 24k map. We could nitpick about some of these numbers, but this should give you some feeling for the relative usefulness of maps vs aerial imagery.

jaybo

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Re: Birds Eye View
« Reply #8 on: March 24, 2013, 11:38:11 AM »
It is raster imagery. That's a fancy way of saying "pictures".

True, but to elaborate, the "pictures" will be georeferenced so that the GPSr can show your position accurately with reference to the imagery, so the imagery and the vector map will occupy the same place on the ellipsoid we call "The Earth".

It's a bit tedious but you can use any .jpg imagery by georeferencing it to the map that is displayed.  You have to make the image semi-transparent then match features on the image to the same area on Google Earth, stretching it until they overlay properly.  Once that's done you save it and send it to the GPSr as a "custom map".

I use it for trail maps that are provided by organizations so that I can see things like traiheads, markers, etc.

Seldom

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Re: Birds Eye View
« Reply #9 on: March 29, 2013, 12:02:08 PM »
All true, jaybo, but Birsdeye .jnx format has a lot fewer limitations.

 

anything